what is obligate and facultative mutualism?

1. In obligate mutualism, one organism cannot survive without the other. This term is easy to remember because both organisms are obligated, or forced to, rely on one another.

An example of obligate mutualism is the relationship between ants and the Acacia plant. The plant provides food for the ant, as well as shelter. In return, the ants defend the plant from other herbivores, or organisms that eat plants, as well as remove other plants from the vicinity of their plant so it can grow better.

Another example is the mycorrhizal  fungi that live on plant roots. The plant roots take advantage of the increased water uptake from the fungi, and the fungi get nutrients from the plant.

           2.Facultative mutualism refers to a biological relationship in which both organisms benefit from the association, but the relationship is not essential. If the organisms must live mutually, then instead of being facultative mutualism, it is called obligate mutualism

An example of organisms that experience facultative mutualism would be aphids and ants. Both aphids and ants are capable of living completely separately. However, when the two insects live in the same area, the ants protect the aphids from predation, and the aphids provide a sugary fluid that the ants can live off of.

Another common example of facultative mutualism is the relationship between small cleaner fish and large fish. Neither of the species need to live together, but the smaller fish can feed off of the parasites on the larger fish. In this case, the small fish are gaining nutrition, and the large fish are receiving protection from parasites.

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